This is a second revised application for competitive renewal for the UCSF Biology of Infectious Diseases Training Program to train physician-scientists for productive careers in fundamental scientific investigations of infectious diseases. Infectious diseases are the third most common cause of death in the United States, despite widespread availability of antibiotics, vaccines, and high standards of public health. Worldwide, infectious diseases are the leading cause of death. Emergence of new pathogens, re-emergence of old ones, increasing resistance to antimicrobials, and pressures of globalization have broken down barriers and contributed to the spread of infectious diseases. Strategies to contain and control the spread of infectious diseases increasingly will rely on strong epidemiologic and population-based approaches and advances in basic research resulting from applications of discoveries in the fields of genomics, microbial pathogenesis, and immunology. The UCSF Biology of Infectious Diseases Training Program, which is modeled according to Infectious Diseases Society of America guidelines and recommendations, features two training tracks, a Basic Investigator Track and a Clinical Investigator Track. These two tracks provide the structural framework for acquisition and translation of research tools, skills, and experiences and for cultivating the scientific creativity that are essential for a successful research-oriented career. The two-track structure also affords the opportunity for interdisciplinary exchange and interactions. The program benefits from a well-established didactic infrastructure and an interactive faculty who direct research programs offering a rich and diversified training environment of exceptional depth and quality. Training is focused on MD and MD-PhD applicants, but PhD post-doctoral candidates are also accepted. In existence for only five years, the program has had considerable success in transitioning trainees to independent sources of research funding and starting them on promising career trajectories. This revised application features an innovative plan to recruit underrepresented minority trainees into the program;viewed as the weakness of the previous version, we believe this plan represents a major strength of the revised proposal. Relevance: The proposed training program is highly relevant to public health, a major concern of which is the control of infectious diseases. We will be training the next generation of medical scientists who will have responsibility for public health and devising strategies to contain the threats posed by infectious agents, scientists who will conduct the studies needed to identify new agents, and those who will discover approaches and therapies to overcome them.